Coil clamping device for a transformer



Der:e l, 95@ H. B. HANSEN ET AL COILCLAMPING DEVICE FOR A TRANSFORMER Filed Oct. 4, 1954 .H M J u@ i 0 1.1mm, cada Y n WLG. \9 It. wm 0k Had .CNW

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United States Patent i COIL CLAMPING DEVICE FOR A TRANSFORMER Harding B. Hansen, Eim Grove, Sten S. Stenersen, Milwaukee, William C. Sealey, Wauwatosa, and Karl P. Wiederkehr, Elm Grove, Wis., assigriors to Allis- Chalmers Manufacturing Company, Milwaukee, Wis.

Application October 4, 1954, Serial No. 459,894

Claims. (Cl. 336-197) This invention relates in general to transformers and is directed particularly to an improved clamping device operable from outside of the transformer tank for clamping the coils and insulation of the winding assembly securely with respect to the transformer tank after the core and winding assembly have been enclosed by the tank.

lt has been the practice for many years in constructing transformers to make the core and winding assemblies as a complete unit separate from the transformer tank. In such construction it is possible to provide clamps associated with the core assembly for holding the coils and insulation in place to form a rigid winding assembly which will not shift or vibrate when the transformer is energized.

To obtain the full benefit of the insulation between the coils, the moisture content of the insulation must be relatively low. Because of this, most winding assemblies after they are assembled are subjected to some type of drying out process which reduces the moisture content in the insulation to a predetermined level. The drying out process results in some shrinkage of the insulation causing the coils of the assembly to become loose. It is therefore necessary after the drying out process to readjust the coil clamps in order to take up the slack caused by the shrinkage of the insulation. When t-he core and winding assemblies are independent of the tank, the coil clamps are readily accessible and it is a simple matter to retighten them just prior to tanking the core and winding assemblies.

Recently a different type of construction for relatively large transformers has become necessary because of weight and size limitations of transportation and handling facilities. In order to increase the rating of the transformer without increasing its size and weight, the core assembly is made an integral part of the transformer tank. In such a transformer the insulation in the winding assembly must be dried out after the transformer is assembled and as before the winding assembly must be reclamped after the drying out process.

Previous suggested devices for clamping the winding assembly cannot be used because after the transformer is assembled, clamps associated with the core would be inside the transformer tank and no longer readily accessible. Therefore, a different clamping device must be provided which is operable from outside of the tank.

According to the present invention, a new and improved clamping device is provided for a transformer in which the core assembly forms an integral part of the tank. The improved clamping device comprises a plurality of jack bolts which extend through the tank wall of the transformer at spaced intervals and which on being turned cause a rigid jack plate to exert a clamping pressure on the winding assembly. Means are provided to maintain the plate in a predetermined position with respect to the tank wall while the transformer is being assembled and during the drying out process.

. To prevent the transformer tank from leaking around the jack bolts when the tank is filled with oil, each bolt Patented Dec. 11, 1956 when in the nal clamping position is sealed to the tank around the perimeter of the bolt. The uid tight seal also maintains the bolt in its final clamping position and prevents it from turning loose.

It is therefore an object of the present invention to provide an improved coil clamp to tightly clamp the coils of the winding assembly after the transformer is assembled.

Another object of the present invention is to provide an improved coil clamp for a transformer in which the core assembly forms an integral part of the transformer tank.

A further object of the present invention is to provide an improved coil clamp operable externally of the transformer tank to tightly clamp the enclosed Winding assembly in position with respect to the tank.

Objects and advantages other than those mentioned above will be apparent from the following description when read in connection with the drawing in which:

Fig. 1 is a view in elevation of a transformer embodying the improved clamping device;

Fig. 2 is an enlarged View in section of the transformer shown in Fig. l taken along the lines Il-ll;

Fig. 3 is an enlarged partial view in section of the transformer shown in Fig. l taken along lines III-III; and

Fig. 4 is an enlarged view in section of a modication of the clamping device shown in Fig. 3.

Referring to the drawing and particularly to Fig. 1 thereof, the improved clamping means is illustrated with reference to a transformer 10 in which the core assembly 11 forms an integral part of the transformer tank 12. The transformer tank contains the core assembly 11 and the winding assembly 13 which may be immersed in an insulating medium such as oil or other suitable insulating fluids.

Transformer tank 12 comprises two sections, 16, 17 each of which is rectangular in shape. The core assembly 11 in this instance is of the shell type construction and comprises a plurality of stacked laminations 18 4held together with suitable end frames 19 and 20. Winding assembly 13 is of the usual type employing disk type coils 21, coil spacers 22 and insulation 23 between adjacent coils. Winding assembly 13 is disposed on the center leg 24 of the magnetic core and is held in position in the transformer tank by means of the clamping device designated generally by reference character 25.

The clamping device comprises a pair of similar jack plates 27, 28 and a plurality of jack bolts 29 which extend through the transformer tank and are in threaded engagement therewith. Jack plates 27 and 2S are disposed parallel to the coils 21 of the winding assembly.

Means are provided for positioning the jack plates in a predetermined position with respect to the tank wall. In the preferred embodiment guide sleeves 30 are fixed to each jack plate at predetermined spaced intervals and these sleeves extend through apertures 31 in the tank wall. The end portion of each jack bolt 29 is disposed in a sleeve 30 and may be in sliding engagement with the inner surface 32 thereof. The outer surface 33 of sleeve 30 is in sliding engagement with the portion of the tank which defines aperture 31. By turning the jack bolts any desired pressure may be applied to the winding assembly 13.

Where the jack plates are metal it is preferable to use a noncompressible insulating member between the jack plate and the winding assembly. As shown, noncompressible insulating members 36, which are preferably made of Masonite, are disposed between the winding assembly 13 and jack plates 27 and 28.

The operation of the improved clamping device and its advantage over clamping devices used in the prior.. art

is more readily seen when consideration is given to the manner in'which the transformer shown in Fig. 1 is assembled. The tank of the transformer is made in two separatel sections .16. andf17, each having a rectangular open end. Channel members are welded adjacent Vto the edges of the open ends of each section in order to provide the end frames 19 and 20 for c ore assembly 11. One of the sections, for example section 17, is then disposed, with the end frame 19 welded thereto, in a hori-V zontal position.. T he jack plate 27. which in this instant is in the shape of a half circle, is placed in section 17 of the tank and positioned parallel to the wall 38 of the tank by means of guide sleeves 30' which are welded to the jack plate 27 and extend in sliding engagement through apertures 31 in the tank wall. The platel 27' is held in lthis position temporarily by means of bolts 39 which are threaded into the ends of the jack bolts 29.

The winding assembly 13, comprising the plurality of disk type coils 21, coil spacers 22, and insulation 23, is assembled independently as a unit and held together prior to insertion in the tank by temporary clamps. The winding assembly is lowered into the tank and the temporary clamps on that part of the winding are removed. When the winding assembly 13 is properly positioned with the axis of the winding disposed a predetermined distance above the horizontally disposed end frame 19, the jack bolts 29 are tightened to clamp the lower half of the winding iirmly with respect to section 17 of the tank. The upper half of the winding assembly still is clamped by the temporary clamps. Since the end frame 19 is disposed horizontally it is a very simple procedure to stack the laminations of the core around the winding on end frame 19. When the laminations 18 are stacked to the correct height the other section 16 of the tank, which is provided with a jack plate 28 and jack bolts 29 similar to section 17, is lowered over the upper portion of the winding assembly 13 and at the same time the temporary clamps holding the upper portion of winding assembly are removed. The upper end frame 20 is disposed in registry with the lower end frame 19 and the pressure on the laminations 18 between the end frames 19 and 20 is adjusted to a predetermined value. When the correct pressure is obtained on the laminations 18 a banding plate 60 is welded around the perimeter of the end frames to clamp the laminations 1S in place. The banding plate 60 in addition to maintaining the predetermined pressure on the laminations of the core, also completes the transformer tank.

After the banding plate 60 is welded in place the winding assembly 13 is clamped firmly in position by adjusting7 the jack bolts 29. With the complete winding assembly clamped tightly with respect to the transformer tank, the transformer may be raised to its normal 0perating position as illustrated in Fig. l, and the winding assembly 13 dried out by any of the well known methods. As the moisture in the windingy assembly 13 decreases during the drying out process and the insulation 23 tends to shrink, the jack bolts 29 are periodically adjusted to maintain the desired clamping pressure on the winding assembly.

After the winding assembly has been dried to a predetermined extent and the jack bolts adjusted to obtain the desired clamping pressure on the' winding assembly, the bolts 29 may be sealed with respect to the tank to prevent the transformer from leaking when filled with oil.

As shown the jack bolts 29 are sealed with respect to the transformer tank by providing a weld 62 between the bolt and the tank around the perimeter of the bolt. Besides providing a fluid type seal, the weld maintains the bolt 29 in the final clamping Vposition land prevents it from turningloose.l Ifdesired the portion of the jack bolt 29 extending past the weldronthe outside of the transformer may then be burned offas shown in Fig. 4 to-give the transformer tank a finished appearance.

It should be apparent to those skilled in the art that the number of jack bolts may be either increased or decreased from the number shown depending on particular conditions and the clamping pressure required on the winding assembly. It should also be apparent that the clamping devices may be provided on opposite sides of the tank. However, satisfactory results have been achieved byl using the improved clamping device on one` side of the tank, while the opposite side of the tank serves as a back support against which the winding assembly is clamped.

While only one embodiment of the present invention has been illustrated it will be apparent to those skilled in the art that modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

lt is claimed and desired to secure by Letters Patent:

1. A transformer comprising a magnetic core, a winding assembly comprising a plurality of disk coils disposed on said core with insulation disposed between adjacent coils, a tank integral with said magnetic core and cooperating therewith to completely enclose said winding assembly, and a clamping device operable from outside of said tank after said transformer is assembled for clamping said coils and said insulation of said winding assembly in a fixed position with respect to said tank, said clamping device comprising a rigid plate disposed' within said tank parallel to said coils, means comprising a guide sleeve attached to said plate and extending in sliding engagement through an aperture in said tank wall for positioning said plate in a predetermined position with respect to said tank, and a jack bolt extending in threaded engagement through said tank wall to cause one end of said bolt to abut said plate when said bolt is turned to cause said plate to move to securely clamp said coils and said insulation in a fixed position in said tank.

2. A transformer comprising a magnetic core, a winding assembly comprising a plurality of disk coils disposed on said core with insulation disposed between adjacent coils, a tank including a wall member disposed parallel to said coils, said tank cooperating with said magnetic core to completely enclose said winding assembly, and clamping means operable from outside of the tank after said transformer is assembled for clamping said coils and said insulation of said winding assemblyl in a iixed position with respect to said tank, said clamping means comprising a rigid plate member disposed within said tank parallel to said coils, means for positioning said plate member in a predetermined position with respect to said wall member comprising a guide sleeve fixed to one of said members and extending through an aperture in said other member in sliding engagement therewith, and a jack bolt extending in threaded engagement through said wall member to cause one end of said bolt to abut said plate when said bolt is turned to cause said plate member to move to securely clamp said coils and said insulation in a fixed position in said tank.

3. A stationary induction apparatus comprising a magnetic core, a winding assembly comprising a plurality of disk coils and insulation disposed on said core, a tank integral with said core and cooperating therewith to completely enclose said assembly, and an externally operable clamping device for clamping said coils and insulation firmly with respect to said tank, said clamping device comprising a rigid plate disposed within said tank intermediate said assembly and said tank, a guide sleeve xedly attached to said plate with the axis of said sleeve normal to said plate, an aperture deiined by a rstportionofsaid tank wall for receiving said sleeve in sliding engagement therewith to position said plate parallel to the plane of said coils, and a jack bolt disposed coaxially with respect to sai-d sleeve with one end abutting said plate, the other end of said bolt extending in threaded engagement through a second portion of said tank to cause said plate to move to clamp said coils and insulation when said bolt is turned.

4. A transformer comprisirg a magnetic core, a winding assembly comprising a plurality of disk coils and insulation disposed on said core, a tank integral with said core and cooperating therewith to completely enclose said assembly, and an externally operable clamping device for clamping said coils and insulation firmly with respect to said tank, said clamping device comprising a rigid plate disposed intermediate said assembly and a wall portion of said tank and parallel to the plane of said coils, a guide sleeve ixedly attached to said plate with the axis of said sleeve normal to said plate, means xed with respect to said wall portion for receiving said sleeve to position said plate with respect to said assembly, a jack bolt extending in threaded engagement through said tank wall and disposed with one end of said bolt in force transmitting relationship with said plate whereby said plate is moved toward said assembly to clamp said coils and insulation when said bolt is turned.

5. An externally operable device for clamping a plurality of disk coils and insulation within an enclosing tank of a transformer in which the magnetic core forms an integral part of said tank, said device comprising a rigid plate disposed parallel to the plane of said coils intermediate said assembly and a wall portion of said tank, a plurality or" guide sleeves lixedly attached to said plate in predetermined spaced relationship, each of said sleeves disposed with its axis normal to the face of said plate, means associated with said wall portion for receiving said sleeves to position said plate with respect to said assembly, and lindividual jack bolts associated with different ones of said sleeves, each of said bolts extending in threaded engagement through a wall portion of said tank with the ends of said bolts disposed in their associated sleeves whereby said plate is moved against said assembly by a turning action of said bolts.

References Cited in the le of this patent UNITED STATES PATENTS 1,224,225 Sieber May l, 1917 1,255,947 Thordarson Feb. 12, 1918 1,435,265 Thompson Nov. 14, 1922 

